On Mon, 6 Jul 2015 21:09:36 -0700 (PDT), you wrote: >I would like to use the BBB to measure the voltage on two battery banks (12V >and 24V). The batteries can go well above the nominal voltages however to 15 >and 30 volts at max respectively. In addition to using a resistive voltage >divider to step down the voltages to the 1.8V required by the ADC is there a >way to ensure that the voltage never excedes 1.8? I've been reading around >about zener diodes and it seems like they would work, but I'm not quite sure >about the implementation. Any advice?
If you run the voltage through a non-inverting op amp that is powered at 1.8 volts + and ground, then the output voltage can never exceed the supply voltage. The op amp should be capable of rail to rail operation. The problem with zeners and straight diodes is that the voltage can exceed the nominal voltage if there is too much (not likely here), but also that the impedance of the diode must be compensated for. Also make sure that the measurement range (depending on reference and ADC setup) does not saturate before your maximum desired voltage. I suspect that 1.0 volts maximum may be typical. (It is on an Xmega depending on the choice of reference). Harvey -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
